i want to add every new json data which i get from this api but it updates the files instead of appending it what to do

I want to add every new json data which I get from this api but it updates the files instead of appending it what to do

Code

import requests
import json

r=requests.get(url="http://api.open-notify.org/iss-now.json")
a=r.json()

latitude=a["iss_position"]["latitude"]
longitude=a["iss_position"]["longitude"]
timestamp=a["timestamp"]

new_data={
    "timestamp": timestamp,
    "message": "success",
    "iss_position": {
        "latitude": latitude,
        "longitude": longitude
    }
}

with open("./35/test.json",mode="r") as data_file:
    load=json.load(data_file)
    load.update(new_data)
with open("./35/test.json",mode="w") as data_file:  
    json.dump(load,data_file,indent=4)

Output

I was expecting this code will do this

{
    "timestamp": 1690471995,
    "message": "success",
    "iss_position": {
        "latitude": "-40.3966",
        "longitude": "172.0519"
    }

"timestamp": 1690472149,
    "message": "success",
    "iss_position": {
        "latitude": "-45.6057",
        "longitude": "-176.9845"
    }
}

to my test.json file but it does not append rather it just keeps on updating the old one

Because you're writing over the same keys; dictionaries don't allow multiples of the same key.

One work around would be to have unique keys associated with each data entry, for example the timestamps:

new_data = {
    'timestamp_ ' + str(timestamp): {
        "timestamp": timestamp,
        "message": "success",
        "iss_position": {
            "latitude": latitude,
            "longitude": longitude
        }
    }
}

This just requires another level of nesting; each data entry is now associated with a specific timestamp.